Welcome to Flyertalk, adidodds.

I think the confusion surrounds the difference between miles in your account and miles flown during the year.

Most airlines offer some sort of 'elite' level for flyers who have their butt in a seat on that particular airline for 25,000-50,000-100,000 miles in a year (some airlines are 25/50/75, Alaska is 15/35). Those levels tend to offer bonus mileage, first class upgrades, and other special services and perks.

No airline that I know of offers you any special perks for high mileage balances in your account. Those miles can be used for awards -- feel free to make use of them!

One other distinction to note is that some airlines offer lifetime elite status based on miles flown. American offers that status based on total miles earned in by you in their program (not total mileage balance in your account at any one time). For more on lifetime status, please see:
http://www.flyertalk.com/forum/Forum1/HTML/008409.html